<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>呼吸灯</title>
    <link rel="stylesheet" href="../common.css">
</head>
<style>
    html, body {
        height: 100%;
    }
    .wrap {
        height: 100%;
        background-color: black;
        position: relative;
    }
    .breath {
        height: 80px;
        width: 80px;
        border-radius: 50%;
        background-color: #fff;
        position: absolute;
        left: 50%;
        top: 50%;
        margin-top: -40px;
        margin-left: -40px;
        box-shadow: 0 0 20px yellow;
        /* opacity: 0.5; */
        animation: change 5s infinite linear alternate;
    }
    @keyframes change {
        from {
            opacity: 0.8;
        }
        to {
            opacity: 0.3;
        }
    }
</style>
<body>
    <div class="wrap">
        <div class="breath"></div>
    </div>
</body>
</html>